Biosensor having nano wire and manufacturing method thereof

ABSTRACT

There is provided a biosensor capable of increasing a detecting sensitivity of a target substance by using a nano wire having excellent electrical characteristics and by immobilizing a receptor of the target substance to be detected on a substrate which is disposed between a nano wire and another nano wire and a method for manufacturing the same. A biosensor according to the present invention can be manufactured with an arrangement in which the nano wire is selectively arranged on a solid substrate in a matrix and, therefore, many materials can be detected at the same time. Particularly, since the degradation of electrical characteristics of the nano wire can be prevented in the present invention, a target substance is very sensitively detected through a small amount thereof.

TECHNICAL FIELD

The present invention relates to a biosensor using a nano wire and a method for manufacturing the same; and, more particularly, to a biosensor capable of increasing a detection sensitivity of a target substance by using a nano wire having excellent electrical characteristics and by immobilizing a receptor of the target substance to be detected on a substrate which is disposed between a nano wire and another nano wire and a method for manufacturing the same.

BACKGROUND ART

Nano-sized materials come into the limelight these days because of their excellent electrical, optical, and mechanical properties. The research that has been being so far progressed about the nano structure shows a possibility as advanced materials for the optical devices based on the new phenomenon like the quantum size effect. Particularly, in case of the nano wire, it is highlighted as the new optical device materials as well as a single electron tunneling device.

The carbon nanotube, as a typical example of the nano wire, is in a tubular form and has a structure in which one carbon atom is covalently bonded to other carbon atoms in hexagonal honeycomb structure. The diameter of the carbon nanotube is exceedingly small to a nano-scale. Particularly carbon nanotube is known as a perfect material with remarkable mechanical property, the electrical selectivity, the field emission or the high-efficiency hydrogen storage.

Recently, high performance biosensors have been developed by using the nano wire such as the carbon nanotube. The reason why the nano wire like the carbon nanotube is used for a biosensor is that it is known to be biocaompatible and labeling is not required and a reaction can be created in the water phase without the deformation of a protein. That is, a fluorescent material, an isotope, or the like has been used for detecting the target agent in conventional biomolecule detecting methods; however, the materials such as the fluorescence or the isotope are very harmful to the human body and the detection procedure is moreover complicate. If the electrical characteristic of the nano wire is used at the time of detection, it has an advantage that it is not harmful to health and it can exactly detect the reaction results.

However, in the conventional biosensor using the existing nano wire or the carbon nanotube, there is a problem in that the resistance increases, the electrical characteristic is degraded, and the detection sensitivity is also degraded consequently, especially in binding a material, which can directly react on the nano wire or the carbon nanotube, to a biomaterial. Moreover, there is a problem in that the electrical characteristic of each nano wire is transformed at the time of plating a polymer layer on a surface of the nano wire or directly immobilizing the biomaterial on the surface of the nano wire through a linker molecule.

Therefore, a demand for a high sensitivity biosensor, in which the electrical characteristic is not degraded, has increased with the excellent and convenient electrical characteristics of the nano wire.

DISCLOSURE

Technical Problem

An embodiment of the present invention is directed to providing a biosensor which can be used for a specific protein scanning, a diagnostic for cancer, a blood sugar measurement, a harmful virus scanning and an environmental toxic material scanning, etc., and which has excellent electrical characteristics and high detection sensitivity.

Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof.

Technical Solution

In accordance with an aspect of the present invention, there is provided a biosensor, including: a solid substrate; at least one signal transducer which is arranged in a matrix and has nano wires to which electrodes are adhered; and at least one signal sensing part which is disposed in the vicinity of the nano wires, wherein a receptor to be bound to a target substance is adhered to the signal sensing part.

In accordance with an aspect of the present invention, there is provided a method for manufacturing a biosensor including the steps of: integrating nano wires on a surface of a solid substrate; coating electrodes with a polymer after forming the electrodes at both ends of each of the nano wires; adhering functional groups on the surface of the solid substrate between the nano wires; and immobilizing a receptor which is bound to a target substance through the functional groups.

Moreover, the present invention provides a method for detecting a target substance connected to a receptor using a bio sensor.

Further, the present invention provides a nano platform including at least one bio sensor.

In the present invention, “nano wires” includes a hollow tubular type nano tube, an inside-filled nano wire and a nano rod.

Advantageous Effects

A biosensor according to the present invention can be manufactured with an arrangement in which the nano wire is selectively arranged on a solid substrate in a matrix and, therefore, many materials can be detected at the same time. Particularly, since the degradation of electrical characteristics of the nano wire can be prevented in the present invention, a target substance is very sensitively detected through a small amount thereof. Moreover, since the nano wires according to the present can be assembled with an arrangement in which the nano wires are selectively arranged on a solid substrate in a matrix, they can be employed as a sensor array which can detect, at the same time, many materials through the various processes. This biosensor can be usefully employed for the diagnostic of cancer, the blood sugar measurement, the harmful virus scanning and the environmental toxic material scanning, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a biosensor manufacturing process according to the present invention.

FIG. 2 is a schematic diagram illustrating a structure of a biosensor according to the present invention.

FIG. 3 is an atomic force microscope photograph of the biosensor to immobilize biotin on a substrate surface according to one embodiment of the present invention.

FIG. 4 is a graph illustrating a current characteristic after administering streptavidin of 100 nM to the conventional biosensor.

FIG. 5 is a graph illustrating a current characteristic after administering streptavidin of 1 nM to the biosensor in which the biotin is immobilized according to the present invention.

FIG. 6 is a nano platform that is manufactured by the biosensor according to the present invention.

BEST MODE FOR THE INVENTION

The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.

A biosensor using a conventional nano wire has a structure in which a receptor capable of catalyzing or being bound to a target substance is directly immobilized on the nano wire. However, the biosensor according to the present invention is characterized in that a receptor is immobilized in the vicinity of the nano wires, i.e., on a surface of a substrate between one nano wire and the other one.

The biosensor according to the present invention includes a solid substrate, at least one signal transducer which is arranged in a matrix and has nano wires to which electrodes are adhered, and at least one signal sensing part which exists in the vicinity of the nano wires and to which a receptor to be bound to a target substance is adhered.

The above-mentioned solid substrate is preferably a substrate which has an insulating surface, such as a silicon or glass substrate, and the silicon substrate typically includes, but not limited to, a silicon oxide film (SiO₂) in the present invention.

The biosensor according to the present invention includes the signal sensing part and the signal transducer disposed on the surface of the solid substrate. The signal sensing part is a portion where a physical or chemical change is caused by the reaction of the receptor or a biochemical substance having an ability to detect the target substance and the signal transducer is a portion where an quantitative analysis of the signal from the signal sensing part is made by using a physical or chemical conversion apparatus having electrodes, etc.

The signal transducer of the biosensor according to the present invention is made of the nano wires which are arranged on the surface of the solid substrate in the matrix and the electrodes are adhered to both ends of the nano wires. The electrodes, which connect the signal transducer to an external signal supplying circuit and a sensing circuit, function as contact junctions to make electrical characteristics observed. The physical and chemical reaction caused in the signal sensing part brings about the change of the electrical characteristic of the signal transducer and it is possible to detect this change through the adhesion junctions at an outside. Each of the electrodes consists of a double structure of a conductive metal and an adhesion metal and the electrodes can be successively deposited by an equipment such as a thermal evaporator, a sputter, or an E-beam evaporator, etc. The adhesion metal is in contact with the nano wire firstly and the conductive metal may be adhered to the adhesion metal when the adhesion metal has the strong binding force with the surface. It is preferable that a metal, which has the excellent electrical contact characteristic with the nano wire and the strong adhesion to the surface for the physical robustness, such as titanium or chrome, are preferably used as the adhesion metal. The conductive metal can be employed by a high conductivity metal without any limitation, especially Au in the preferred embodiment of the present invention.

Moreover, the signal sensing part of the biosensor according to the present invention is disposed in the vicinity of the signal transducer including the nano wires and the electrodes and the receptor which is capable of being bounded to the target substance is adhered to the signal sensing part.

The receptor is adhered to the surface of the solid substrate by the functional group and the receptor is, but not limited to, at least one selected from the group consisting of enzyme-substrate, ligand, amino acid, peptide, protein, nucleic acid, lipid and carbohydrate.

The functional group connecting the receptor to the solid substrate is, but not limited to, at least one selected from the group consisting of an amine group, a carboxyl group and a thiol group.

The target substance to be detected is, but not limited to, at least one selected from the group consisting of a protein, a nucleic acid, oligosaccharide, an amino acid, a carbohydrate, a solution gas, a sulfur oxide (SOx) gas, a nitrogen oxide (NOx) gas, a residual agricultural chemical, a heavy metal and an environmental toxic material.

The nano wires deposited on the signal transducer of the biosensor according to the present invention is, but not limited to, at least one selected from the group consisting of a carbon nanotube, a silicon nano wire, and a zinc oxide nano wire and a vanadium oxide nano wire.

More specifically, the biosensor according to the present invention will be described below referring to FIG. 2.

First, one or more signal transducers 102 exist on the solid substrate 107 and the signal transducers 102 include the carbon nanotubes 104 and the electrodes 105 which are disposed at both ends of the carbon nanotube 104. The electrodes 105 are coated with a polymer 106. The signal transducers 102 are arranged on the solid surface in a matrix and the signal sensing part 101 is made by a portion in which the carbon nanotube 104 are not formed, that is, a portion between the signal transducers 102. The receptors 103 are adhered to the signal transducers 102 by the functional groups.

Meanwhile, the present invention provides a method for manufacturing the biosensor. The method for manufacturing the biosensor includes the steps of: integrating nano wires on a surface of a solid substrate; coating electrodes with a polymer after forming the electrodes at both ends of each of the nano wires; adhering functional groups on the surface of the solid substrate between the nano wires; and immobilizing receptors which are bound to a target substance through the functional groups.

To manufacture the biosensor according to the present invention, first, the nano wires are integrated on the surface of the solid substrate such as a silicon oxide film or a glass substrate. The integration of the nano wires on the surface of the substrate can be implemented by the general methods which are well known to those skilled in the art to which the subject pertains. Particularly, in the method for integrating the nano wires according to the preferred embodiment of the present invention, the surface of the solid substrate is patterned by a slippery molecular layer and the nano structure material to be adhered is then slid onto the surface of the solid substrate from the slippery molecular layer so that the nano wires are adhered directly on the surface of the solid substrate.

Next, the electrodes are deposited at both ends of each of the nano wires. The deposition of the electrodes is carried out by a thermal evaporator, an E-beam evaporator or a sputter which is typically used in manufacturing electrodes of semiconductor devices. The deposited electrodes are coated with the polymer in order to reduce a leakage current. After forming the signal transducers made of the nano wires and the electrodes, the functional groups are adhered on the surface of the solid substrate and between one nano wire and an adjacent nano wire and the receptors, which are capable of being bound to the target substance, are immobilized on the adhered functional groups.

Being different from the conventional biosensor, the biosensor according to the present invention is characterized in that the functional groups are selectively adhered on the surface of the solid substrate on which the nano wires are not integrated. In the present invention, in order to selectively adhere the functional groups on the surface of the solid substrate on which the nano wires are not integrated, a compound bearing a silane group is used. Especially, 3-aminopropyltriethoxysilane (APTES) is used in the present invention. If the ethoxylated group within the silane group meets with —OH on the silicon oxide film or the glass surface, the ethoxylated group is detached from the silane group and it is combined with the silicon surface with strong covalent bonds. In the cleaning process, molecules which are not combined with the covalent bonds are altogether gone away. Therefore, the functional groups are adhered to the surface in which the nano wires are not selectively integrated. Concretely, it is preferable that the substrate, on which the nano wires are integrated, is dipped in a compound having the silane group for 5 to 20 minutes. If the substrate is dipped for the above-mentioned time, the functional group can be more selectively and effectively adhered to the surface on which the nano wires are not integrated.

Generally, the nano wires are classified into various kinds of chemical structures of the surface and these chemical structures are completely different from each other. For example, the carbon nanotube consists of the carbon lattice structure of a hexagon and the silicon nano wire is composed of a silicon crystalline structure. Besides, each of the nano wires, such as a zinc oxide nano wire, a vanadium oxide nano wire and so on, has a different chemical property of the surface. When the receptor capable of being bound additionally to the target substance is immobilized after various kinds of nano wires are integrated on the solid surface, a different chemical process has to be applied to each nano wire and this process has to satisfy the complicated conditions. That is, the receptor immobilization technique, in which the receptor is immobilized by the non-covalent bonds based on the hydrophobic interaction between a phenyl group or an alkyl group and the carbon nanotube or by the covalent bonds to attack a carboxyl group on the surface of the carbon nanotube, is used in case of the carbon nanotube. In case of a silicon nano wire, the silane group is used. This has a problem in that it takes a lot of time to immobilize the receptor after the integrated circuit processing in a mass product of the nano wires and the processes are very complicated. Moreover, a process of a specific nano wire can be very injurious to other nano wires. However, in the present invention, the receptors capable of being bound to the target substance to be detected are not adhered directly to the nano wires, but immobilized in the vicinity of the nano wires, so that it is possible to immobilize the receptors regardless of the kinds of the nano wires. As a result, the present invention has the advantage of the cost-effectiveness in time and resources.

On the other hand, a nano platform in which at least one biosensor, as described above, is adhered to the substrate, is provided in the present invention.

Hereinafter, the present invention is exemplarily illustrated with an embodiment.

However, the following embodiment exemplarily illustrates the present invention and the present invention is not restricted to the following embodiment.

EMBODIMENT 1 Manufacturing Biosensor for Detecting Streptavidin

A photoresist pattern is formed on a silicon oxide substrate surface by using the photolithography process. Thereafter, it is dipped in a solution in which octadecyl trichloro silane (hereinafter, referred to ad OTS) (sigma) and ethanol were mixed at a mixed ratio of 1:500 (volume ratio) and the OTS molecular layer is formed on the substrate surface.

The substrate on which the molecular monolayer is formed is dipped in an acetone solution and the photoresist pattern is removed. Subsequently, the substrate is dipped in a carbon nanotube solution of o-dichlorobenzene and the carbon nanotubes are self-assembled on the substrate surface.

Titanium and then Au thin films are deposited on the carbon nanotubes of the substrate and the metals outside the electrode regions are removed by lift-off process. The electrodes are then coated with a polymer like SU-8.

Next, the substrate on which the carbon nanotubes are integrated is dipped in 3-aminopropyltriethoxysilane (APTES) (sigma) solution for 5 minutes and an amine group are selectively attached to the carbon nanotubes on the silicon substrate.

The biosensor for detecting streptavidin is finally manufactured by dipping the substrate, to which the amine group is adhered, in a biotin solution and by binding the amine group on the substrate to the biotin as the receptors.

The biosensor manufacturing process is shown in FIG. 1 and the structure of the finally manufactured biosensor is shown in FIG. 2.

EXAMPLE 1 Detecting Streptavidin

The performance test of the biosensor for detecting streptavidin, manufactured in the embodiment 1, is executed.

After the buffer solution (PBS pH 7.4) is dropt to the conventional biosensor (control group) in which the biotin is not immobilized and the biosensor in which the biotin is immobilized according to the preferred embodiment 1 of the present invention, the voltage of 0.1V is applied to the electrodes disposed at both ends of each electrode of the substrates and a current is sampled according to the time. The results of the current variance with injection of streptavidin and with no injection thereof are shown in FIGS. 4 and 5, respectively.

Referring to FIG. 4, the conventional biosensor (control group) in which the biotin is not immobilized has a constant current even if streptavidin of 100 nM is applied to the biosensor and the time is sufficiently over.

However, Referring to FIG. 5, the biosensor in which the biotin is immobilized according to the present invention has a drastic change of the current after 250 seconds even if streptavidin of just only 1 nM, as a target substance to be detected, is applied to the biosensor. That is, the target substance can be effectively detected with a small amount. Therefore, the high sensitivity of the biosensor of the present invention can be confirmed in FIG. 5.

EXAMPLE 2 Manufacturing Nano Platform for Biosensor

The nano platform is manufactured by using the biosensor manufactured in the above-mentioned embodiment 1 (referring to FIG. 6) according to the present invention. 

1. A biosensor, comprising: a solid substrate; at least one signal transducer which is arranged in a matrix and has nano wires to which electrodes are adhered; and at least one signal sensing part which is disposed in the vicinity of the nano wires, wherein a receptor to be bound to a target substance is adhered to the signal sensing part.
 2. The biosensor of claim 1, wherein the solid substrate is a silicon substrate or a glass substrate.
 3. The biosensor of claim 1, wherein the receptor is adhered to a surface of the solid substrate by functional groups and wherein the receptor is at least one selected from the group consisting of enzyme-substrate, ligand, amino acid, peptide, protein, nucleic acid, lipid and carbohydrate.
 4. The biosensor of claim 3, wherein the functional group is at least one selected from the group consisting of an amine group, a carboxyl group and a thiol group.
 5. The biosensor of claim 1, wherein the target substance is at least one selected from the group consisting of a protein, a nucleic acid, oligosaccharide, an amino acid, a carbohydrate, a solute gas, a sulfur oxide (SOx) gas, a nitrogen oxide (NOx) gas, residual agricultural chemicals, a heavy metal and an environmental toxic material.
 6. The biosensor of claim 1, wherein the nano wire is at least one selected from the group consisting of a carbon nanotube, a silicon nano wire, and a zinc oxide nano wire and a vanadium oxide nano wire.
 7. A method for manufacturing a biosensor comprising the steps of: a) integrating nano wires on a surface of a solid substrate; b) coating electrodes with a polymer after forming the electrodes at both ends of each of the nano wires; c) adhering functional groups on the surface of the solid substrate between the nano wires; and d) immobilizing a receptor through the functional groups which catalyzes or is bound to a target substance.
 8. The method of claim 7, wherein the solid substrate is a silicon substrate or a glass substrate.
 9. The method of claim 7, wherein the receptor is adhered to a surface of the solid substrate by functional groups and wherein the receptor is at least one selected from the group consisting of enzyme-substrate, ligand, amino acid, peptide, protein, nucleic acid, lipid and carbohydrate.
 10. The method of claim 7, wherein the functional group is at least one selected from the group consisting of an amine group, a carboxyl group and a thiol group.
 11. The method of claim 7, wherein the target substance is at least one selected from the group consisting of a protein, a nucleic acid, oligosaccharide, an amino acid, a carbohydrate, a solution gas, a sulfur oxide (SOx) gas, a nitrogen oxide (NOx) gas, a residual agricultural chemical, a heavy metal and an environmental toxic material.
 12. The method of claim 7, wherein the nano wires are at least one selected from the group consisting of a carbon nanotube, a silicon nano wire, and a zinc oxide nano wire and a vanadium oxide nano wire.
 13. The method of claim 7, wherein the step of adhering functional groups on the surface of the solid substrate between the nano wires is carried out by dipping the substrate in a compound having the silane group for 5 to 20 minutes.
 14. A method for detecting a target substance to be bound to a receptor using the biosensor in accordance with claim
 1. 15. A nano platform having at least one biosensor in accordance with claim
 1. 